It is known that a quinoxaline derivative has an antibacterial property (Non-Patent Document 1) and hypoxic cytotoxicity (Non-Patent Document 2).
Moreover, it is reported that a quinoxaline 1,4-dioxide derivative selectively develops toxicity in a hypoxic cell (Non-Patent Document 3). The quinoxaline 1,4-dioxide derivative is subjected to in vivo reduction in a hypoxic state, and converted into a radical compound having high reactivity (disturbance in the cell), and the resultant radicals exert especially strong cytotoxicity in the hypoxic state. Many cancers are solid cancers, capillary vessels of solid cancer tissues are destroyed owing to abnormal cell proliferation, hence the tissues are isolated from other tissues, and neogenesis of blood vessels cannot catch up with the cell proliferation, so that oxygen and nutrition are not sufficiently supplied to the tissues, thereby bringing the tissues into the hypoxic state. Therefore, it can be expected that the present quinoxaline 1,4-dioxide derivative does not much disturb normal tissues to which oxygen is sufficiently supplied, and peculiarly disturbs a seat of disease only.
Heretofore, the quinoxaline derivative is synthesized by Beirut reaction in which a β-diketone compound is added to benzofuroxan in the presence of a basic catalyst such as triethylamine, and then dehydrocyclized. For example, it is reported that to synthesize 2-benzoyl-6,7-dichloro-3-phenylquinoxaline 1,4-dioxide owing to Beirut reaction, a reaction time is 24 hours, and a yield is 36% (Non-Patent Documents 4, 5).    Non-Patent Document 1: Journal of the Pharmaceutical Society of Japan, Vol. 116, No. 6, 491 to 496    Non-Patent Document 2: Oncology Reports 8, 679 to 684 (2001)    Non-Patent Document 3: J. Med. Chem. 1995, 38, 1786 to 1792    Non-Patent Document 4: Heterocycles Vol. 4, No. 6, 1077 to 1082 (1976)    Non-Patent Document 5: Journal of Organic Chemistry Vol. 31, 4067 to 4068 (1966)